Riots at the Manus Island detention centre earlier this month were caused by management's handling of questions posed by asylum seekers, a PNG police report says.

The leaked report, written the day after the second clash - which took place on February 17 - also makes it clear the confrontation occurred inside the detention centre, contrary to information given at the time by Immigration Minister Scott Morrison.

Local police knew as early as February 18 that the clashes occurred within the detention centre.

The report is an internal police document written by Manus Island provincial police commander Alex N'Drasal to update the acting assistant commissioner of police. It was leaked to the media yesterday.

Asylum seekers' questions

Is there a process? What is it?

How long are we going to be here?

When will we have our freedom?

Will transferees who have been deemed refugees in other countries be given priority in processing?

Why is there no PNG Partnership?

Some of the transferees have been interviewed some time ago, what is happening with our process? What is the hold-up?

Will the Australian Government take responsibility for our mental health problems?

The Playfair lawyer said there was a third country option, why can't we be sent to this other country?

Why are our human rights not respected?

The report says in the week before the violence occurred, asylum seekers had submitted 11 questions about the processing of their refugee applications, the conditions of their detention and the authority of those detaining them.

"Is there a process? What is it?" was the first question posed by asylum seekers, police say.

"Who is responsible for us here on Manus - PNG or Australia?" was another question.

"The Playfair lawyer said there was a third country option. Why can't we be sent to this other country?"

Playfair is private company of migration agents and immigration lawyers.

On February 17, management of the detention centre met with asylum seekers to discuss their concerns.

Mr Morrison says asylum seekers were told their only option for resettlement was in Papua New Guinea.

"The asylum seekers were not satisfied with the response given to them by the management last week and that instigated frustrations within several different countries' occupants of the Oscar compound," chief inspector N'Drasal wrote on February 18.

Referring to the second night of rioting, during which an Iranian man was killed, chief inspector N'Drasal wrote: "In the Mike compound the transferees did also protest for that same reason as mentioned for the Oscar compound on Sunday."

Head injuries caused asylum seeker death

The incident report named Reza Berati as the asylum seeker who died in the riot on February 17.

"The cause of death of the Iranian is from the multiple head injuries that could be caused by (a) heavy object, as advised by [the] IHMS (International Health and Medical Services) medical officer who treated the transferee ... and also the police investigator," chief inspector N'Drasal wrote.

However, it cautions that "the investigation still continues to reconfirm the real cause of death" and says more detailed reports will be submitted later.

A spokesman for Mr Morrison says the autopsy has now been completed and an autopsy report is being prepared.

The ABC understands at least one Australian forensic pathologist assisted the Papua New Guinea team investigating Berati's death.

The police report says two seriously injured Iranian men taken to hospital on the night of February 18 were both in their mid-20s. One had back injuries and the other had an abdomen injury.

Police report matches witness accounts

The leaked report about what happened during the rioting matches witness accounts given to the ABC.

It says "the confrontation was between the management of the centre, G4S guards as one party, and the transferees as another party".

"The G4S guards went to stopped (sic) the transferees from rioting at the compound and damaging properties," chief inspector N'Drasal wrote.

G4s guards were "overpowered" and "seriously assaulted" by asylum seekers, according to the police report.

Chief inspector N'Drasal said the PNG police mobile squad "actually fired some warning shots into the air" and he believed the situation could have been worse if not for the mobile squad's actions.

The PNG government is conducting a formal investigation of the two incidents at the Manus Island detention centre but it is not clear when these will be completed.

Australia is doing its own investigation, with the co-operation of the PNG government.

It is due to report back in April, with a progress report by the end of March.